<template>
  <view>
    <view id="_drag_button" class="drag" :style="'left: ' + left + 'px; top:' + top + 'px;'" @touchstart="touchstart" @touchmove.stop.prevent="touchmove" @touchend="touchend" @click.stop.prevent="click" :class="{transition: isDock && !isMove }">
      <image v-if="image" :src="image==''?'./img/icon.png':image" mode="aspectFit" style="width: 100rpx;height: 100rpx;"></image>
      <text v-else>{{ text }}</text>
    </view>
  </view>
</template>
<script>
export default {
    name: 'drag-button',
    props: {
        isDock: {
            type: Boolean,
            default: false
        },
        existTabBar: {
            type: Boolean,
            default: false
        },
        image: {
            type: String,
            default: ''
        }
    },
    data() {
        return {
            top: 300,
            left: 0,
            width: 0,
            height: 0,
            offsetWidth: 0,
            offsetHeight: 0,
            windowWidth: 0,
            windowHeight: 0,
            isMove: true,
            edge: 10,
            text: '按钮'
        }
    },
    mounted() {
        const sys = uni.getSystemInfoSync();
        this.windowWidth = sys.windowWidth;
        this.windowHeight = sys.windowHeight;
        // #ifdef APP-PLUS
        this.existTabBar && (this.windowHeight -= 50);
        // #endif
        if (sys.windowTop) {
            this.windowHeight += sys.windowTop;
        }
        console.log(sys)
        const query = uni.createSelectorQuery().in(this);
        query.select('#_drag_button').boundingClientRect(data => {
            this.width = data.width;
            this.height = data.height;
            this.offsetWidth = data.width / 2;
            this.offsetHeight = data.height / 2;
            this.left = this.windowWidth - this.width - this.edge;
            this.top = this.windowHeight - this.height - this.edge;
        }).exec();
    },
    methods: {
        click() {
            this.$emit('btnClick');
        },
        touchstart(e) {
            this.$emit('btnTouchstart');
        },
        touchmove(e) {
            // 单指触摸
            if (e.touches.length !== 1) {
                return false;
            }
            this.isMove = true;
            this.left = e.touches[0].clientX - this.offsetWidth;
            let clientY = e.touches[0].clientY - this.offsetHeight;
            // #ifdef H5
            clientY += this.height;
            // #endif
            let edgeBottom = this.windowHeight - this.height - this.edge;
            // 上下触及边界
            if (clientY < this.edge) {
                this.top = this.edge;
            } else if (clientY > edgeBottom) {
                this.top = edgeBottom;
            } else {
                this.top = clientY
            }
        },
        touchend(e) {
            if (this.isDock) {
                let edgeRigth = this.windowWidth - this.width - this.edge;
                if (this.left < this.windowWidth / 2 - this.offsetWidth) {
                    this.left = this.edge;
                } else {
                    this.left = edgeRigth;
                }
            }
            this.isMove = false;
            this.$emit('btnTouchend');
        },
    }
}

</script>
<style lang="scss">
.drag {
    display: flex;
    justify-content: center;
    align-items: center;
    color: $uni-text-color-inverse;
    width: 100rpx;
    height: 100rpx;
    border-radius: 50%;
    font-size: $uni-font-size-sm;
    position: fixed;
    z-index: 1000;

    &.transition {
        transition: left 0.3s ease, top 0.3s ease;
    }
}
</style>
